Through Via Structure and Method

ABSTRACT

A method comprises forming a trench extending through an interlayer dielectric layer over a substrate and partially through the substrate, depositing a photoresist layer over the trench, wherein the photoresist layer partially fills the trench, patterning the photoresist layer to remove the photoresist layer in the trench and form a metal line trench over the interlayer dielectric layer, filling the trench and the metal line trench with a conductive material to form a via and a metal line, wherein an upper portion of the trench is free of the conductive material and depositing a dielectric material over the substrate, wherein the dielectric material is in the upper portion of the trench.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/828,110, entitled “Through Via Structure”, filed on Aug. 17, 2015,which is a divisional of U.S. patent application Ser. No. 13/619,233,entitled “Through Via Structure and Method”, filed on Sep. 14, 2012, nowU.S. Pat. No. 9,112,007, each application is incorporated herein byreference.

BACKGROUND

The semiconductor industry has experienced rapid growth due tocontinuous improvements in the integration density of a variety ofelectronic components (e.g., transistors, diodes, resistors, capacitors,etc.). For the most part, this improvement in integration density hascome from repeated reductions in minimum feature size, which allows morecomponents to be integrated into a given area. As the demand for evensmaller electronic devices has grown recently, there has grown a needfor smaller and more creative packaging techniques of semiconductordies.

As semiconductor technologies evolve, three dimensional integratedcircuits have emerged as an effective alternative to further reduce thephysical size of a semiconductor chip. In a three dimensional integratedcircuit, active circuits such as logic, memory, processor circuitsand/or the like are fabricated on different wafers and each wafer die isstacked on top of a packaging component using pick-and-place techniques.Much higher density can be achieved by employing three dimensionalintegrated circuits. In sum, three dimensional integrated circuits canachieve smaller form factors, cost-effectiveness, increased performanceand lower power consumption.

In order to connect electrical circuits in the stacked semiconductordies, through silicon vias are employed to provide a vertical connectionchannel through the body of stacked dies. Through silicon vias can beformed by using suitable techniques. For example, in order to form athrough silicon via, an opening may be formed on an active side of thesemiconductor substrate, wherein the opening extends deeper into thesemiconductor substrate than the active devices of the semiconductorsubstrate. These openings may then be filled with a conductive materialsuch as copper, aluminum, tungsten, silver, gold and/or the like. Afterthe openings have been filled, the backside of the semiconductorsubstrate may be thinned through a thinning process such as a chemicalmechanical polishing process or an etching process. The thinning processis applied to the backside of the substrate until the conductivematerial of the through silicon via is exposed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a cross sectional view of a semiconductor device inaccordance with an embodiment;

FIG. 2 illustrates a semiconductor device after a plurality ofelectrical circuits have been formed in the substrate in accordance withan embodiment;

FIG. 3 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 2 after an opening is formed the substrate in accordancewith an embodiment;

FIG. 4 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 3 after a liner layer is formed on the sidewalls and thebottom of the opening in accordance with an embodiment;

FIG. 5 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 4 after a barrier layer is formed over the liner layer inaccordance with an embodiment;

FIG. 6 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 5 after a seed layer is formed over the barrier layer inaccordance with an embodiment;

FIG. 7 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 6 after a dielectric layer is formed over the seed layerin accordance with an embodiment;

FIG. 8 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 7 after a patterning process is applied to the dielectriclayer in accordance with an embodiment;

FIG. 9 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 8 after a conductive material is filled in the opening inaccordance with an embodiment;

FIG. 10 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 9 after the remaining photoresist layer has been removedin accordance with an embodiment;

FIG. 11 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 10 after an inter-metal dielectric layer is deposited inaccordance with an embodiment;

FIG. 12 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 11 after two additional metallization layers are formedover the first metallization layer in accordance with an embodiment;

FIG. 13 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 12 after a passivation layer is formed on the top of theinter-metal dielectric layer in accordance with an embodiment;

FIG. 14 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 13 after a first polymer layer is formed on the top of thepassivation layer in accordance with an embodiment;

FIG. 15 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 14 after a patterning process is applied to the surface ofthe first polymer layer in accordance with an embodiment;

FIG. 16 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 15 after a seed layer is formed on top of the firstpolymer layer in accordance with an embodiment;

FIG. 17 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 5 after a redistribution line is formed on top of the seedlayer in accordance with an embodiment;

FIG. 18 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 17 after a second polymer layer is formed over thesemiconductor device in accordance with an embodiment;

FIG. 19 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 18 after a patterning process is applied to the surface ofthe second polymer layer in accordance with an embodiment;

FIG. 20 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 19 after a UBM seed layer is formed on top of the secondpolymer layer in accordance with an embodiment;

FIG. 21 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 20 after a second conductive layer is formed on top of theUBM seed layer in accordance with an embodiment;

FIG. 22 illustrates a cross section view of the semiconductor deviceshown in FIG. 21 after an interconnect bump is formed on the UBMstructure in accordance with an embodiment;

FIG. 23 is a cross sectional view of the semiconductor deviceillustrated in FIG. 22 after a thinning process has been applied to thesecond side of the substrate in accordance with an embodiment; and

FIG. 24 illustrates a cross section view of the semiconductor deviceshown in FIG. 23 after a backside contact is formed on the second sideof the substrate in accordance with an embodiment.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the variousembodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the present embodiments are discussed in detailbelow. It should be appreciated, however, that the present disclosureprovides many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative of specific ways to make and use the embodimentsof the disclosure, and do not limit the scope of the disclosure.

The present disclosure will be described with respect to embodiments ina specific context, namely a through via structure of a semiconductorpackage. The embodiments of the disclosure may also be applied, however,to a variety of packages of the semiconductor industry. Hereinafter,various embodiments will be explained in detail with reference to theaccompanying drawings.

FIG. 1 illustrates a cross sectional view of a semiconductor device inaccordance with an embodiment. The semiconductor device 100 is formed ina substrate 102. The substrate 102 has a first side 101 and a secondside 103. A first side interconnection structure 110 is formed over thefirst side 101 of the substrate 102. A second side interconnectionstructure 120 is formed over the second side 103 of the substrate 102.The details of the first side interconnection structure 110 and thesecond side interconnection structure 120 will be described below withrespect to FIGS. 2-24.

The semiconductor device 100 may comprise a plurality of through vias.For simplicity, only one through via 142 is shown in FIG. 1. The throughvia 142 may be divided into three portions. The bottom portion isadjacent to the second side 103 of the substrate 102. The sidewallportions are formed along the sidewalls of the through via opening. Moreparticularly, as shown in FIG. 1, the sidewall portions of the throughvia 142 are coupled between the bottom portion and metal lines 184 and186 of the first metallization layer respectively.

As shown in FIG. 1, there may be three thin layers 122, 124 and 126formed between the substrate 102 and the sidewall portions of thethrough via 142. In accordance with an embodiment, the thin layers 122,124 and 126 are a liner layer, a barrier layer and a seed layerrespectively. The detailed fabrication process of these three thinlayers will be described below with respect to FIGS. 4-6.

The through via 142 may further comprise a middle portion formed betweentwo sidewall portions. The middle portion may comprise a dielectricmaterial. More particularly, the material of the middle portion may bethe same as the material of the first inter-metal dielectric layer 182.The detailed formation of the through via 142 will be described belowwith respect to FIGS. 9-11.

The substrate 102 may be formed of silicon, although it may also beformed of other group III, group IV, and/or group V elements, such assilicon, germanium, gallium, arsenic, and combinations thereof. Thesubstrate 102 may also be in the form of silicon-on-insulator (SOI). TheSOI substrate may comprise a layer of a semiconductor material (e.g.,silicon, germanium and/or the like) formed over an insulator layer(e.g., buried oxide or the like), which is formed in a siliconsubstrate. In addition, other substrates that may be used includemulti-layered substrates, gradient substrates, hybrid orientationsubstrates and/or the like.

The substrate 102 may further comprise a variety of electrical circuits(not shown). The electrical circuits formed on the substrate 102 may beany type of circuitry suitable for a particular application. Inaccordance with an embodiment, the electrical circuits may includevarious n-type metal-oxide semiconductor (NMOS) and/or p-typemetal-oxide semiconductor (PMOS) devices such as transistors,capacitors, resistors, diodes, photo-diodes, fuses and/or the like. Theelectrical circuits may be interconnected to perform one or morefunctions. The functions may include memory structures, processingstructures, sensors, amplifiers, power distribution, input/outputcircuitry and/or the like. One of ordinary skill in the art willappreciate that the above examples are provided for illustrativepurposes only and are not intended to limit the various embodiments toany particular applications.

An interlayer dielectric layer 115 is formed on top of the substrate102. The interlayer dielectric layer 115 may be formed, for example, ofa low-K dielectric material, such as silicon oxide. The interlayerdielectric layer 115 may be formed by any suitable method known in theart, such as spinning, chemical vapor deposition (CVD) and plasmaenhanced chemical vapor deposition (PECVD). It should also be noted thatone skilled in the art will recognize while FIG. 1 illustrates a singleinterlayer dielectric layer, the interlayer dielectric layer 115 maycomprise a plurality of dielectric layers.

FIG. 1 further illustrates a first inter-metal dielectric layer 182formed over the interlayer dielectric layer 115. As shown in FIG. 1,there may be two metal lines 184 and 186 formed in the first inter-metaldielectric layer 182. The through via 142 is coupled to the metal lines184 and 186. In particular, the metal portions of the through via 142and the metal lines 184 and 186 may be formed at the same fabricationstep. The detailed formation of the metal lines and the through via 142will be described below with respect to FIGS. 7-10.

It should be noted while FIG. 1 illustrates metal lines 184 and 186formed in the first inter-metal dielectric layer 182, one person skilledin the art will recognize that more inter-metal dielectric layers andthe associated metallization layers may be used to interconnect theelectrical circuits in the substrate 102 to each other to formfunctional circuitry and to further provide an external electricalconnection. A fabrication process of the semiconductor device 100 havingmultiple inter-metal dielectric layers and the associated metallizationlayers will be described below with respect to FIGS. 2 to 24.

FIGS. 2 to 24 illustrate intermediate steps of fabricating the throughvia shown in FIG. 1 in accordance with an embodiment. The fabricationprocess described below is based upon a via-first fabrication process.However, as one having ordinary skill in the art will recognize that thevia-first fabrication process described below is merely an exemplaryprocess and is not meant to limit the various embodiments. Other viafabrication processes such as via-middle and via-last fabricationtechniques may alternatively be used. In sum, any suitable viafabrication process may be used, and all such processes are fullyintended to be included within the scope of the embodiments discussedherein.

FIG. 2 illustrates a semiconductor device after a variety of electricalcircuits have been formed in the substrate in accordance with anembodiment. The substrate 102 may comprise a variety of electricalcircuits such as metal oxide semiconductor (MOS) transistors (e.g., MOStransistor 200) and the associated contact plugs (e.g., contact plug118). For simplicity, only a single MOS transistor and a single contactplug are presented to illustrate the innovative aspects of variousembodiments.

The MOS transistor 200 is formed in the substrate 102. The MOStransistor 200 includes two drain/source regions 106. As shown in FIG.2, the drain/source regions 106 are formed on opposite sides of a gatestack. The gate stack includes a gate dielectric layer 112 formed overthe substrate 102, a gate electrode formed over the gate dielectriclayer 112 and gate spacers 116. As shown in FIG. 2, there may be twoisolation regions 104 formed on opposite sides of the MOS transistor200.

The isolation regions 104 may be shallow trench isolation (STI) regions,and may be formed by etching the substrate 102 to form a trench andfilling the trench with a dielectric material as is known in the art.For example, the isolation regions 104 may be filled with a dielectricmaterial such as an oxide material, a high-density plasma (HDP) oxideand/or the like. A planarization process such as a CMP process may beapplied to the top surface so that the excess dielectric material may beremoved as a result.

The gate dielectric 112 may be a dielectric material such as siliconoxide, silicon oxynitride, silicon nitride, an oxide, anitrogen-containing oxide, a combination thereof and/or the like. Thegate dielectric 112 may have a relative permittivity value greater thanabout 4. Other examples of such materials include aluminum oxide,lanthanum oxide, hafnium oxide, zirconium oxide, hafnium oxynitride,combinations thereof and/or the like. In an embodiment in which the gatedielectric 112 comprises an oxide layer, the gate dielectrics 112 may beformed by a PECVD process using tetraethoxysilane (TEOS) and oxygen as aprecursor. In accordance with an embodiment, the gate dielectric 112 maybe of a thickness in a range from about 8 Å to about 200 Å.

The gate electrode 114 may comprise a conductive material, such as ametal (e.g., tantalum, titanium, molybdenum, tungsten, platinum,aluminum, hafnium, ruthenium), a metal silicide (e.g., titaniumsilicide, cobalt silicide, nickel silicide, tantalum silicide), a metalnitride (e.g., titanium nitride, tantalum nitride), dopedpoly-crystalline silicon, other conductive materials, combinationsthereof and/or the like. In an embodiment in which the gate electrode114 is poly-silicon, the gate electrode 114 may be formed by depositingdoped or undoped poly-silicon by low-pressure chemical vapor deposition(LPCVD) to a thickness in the range of about 400 Å to about 2,400 Å.

The spacers 116 may be formed by blanket depositing one or more spacerlayers (not shown) over the gate electrode 114 and the substrate 102.The spacer layers 116 may comprise suitable dielectric materials such asSiN, oxynitride, SiC, SiON, oxide and/or the like. The spacer layers 116may be formed by commonly used techniques such as CVD, PECVD, sputterand/or the like.

The drain/source regions 106 may be formed in the substrate 102 onopposing sides of the gate dielectric 112. In an embodiment in which thesubstrate 102 is an n-type substrate, the drain/source regions 106 maybe formed by implanting appropriate p-type dopants such as boron,gallium, indium and/or the like. Alternatively, in an embodiment inwhich the substrate 102 is a p-type substrate, the drain/source regions106 may be formed by implanting appropriate n-type dopants such asphosphorous, arsenic and/or the like.

As shown in FIG. 2, the interlayer dielectric layer 115 is formed overthe substrate 102. There may be a contact plug 118 formed in theinterlayer dielectric layer 115. The contact plug 118 is formed throughthe interlayer dielectric layer 115 to provide an electrical connectionbetween the MOS transistor 200 and the interconnect structure (not shownbut illustrated in FIG. 24) formed over the interlayer dielectric layer115.

The contact plug 118 may be formed by using photolithography techniquesto deposit and pattern a photoresist material on the interlayerdielectric layer 115. A portion of the photoresist is exposed accordingto the location and shape of the contact plug 118. An etching process,such as an anisotropic dry etch process, may be used to create anopening in the interlayer dielectric layer 115.

A conductive liner may be deposited prior to filling the contact plughole. The conductive liner is preferably conformal, and may comprise asingle layer of Ta, TaN, WN, WSi, TiN, Ru and combinations thereof. Theconductive liner may be typically used as a barrier layer for preventingthe conductive material such as copper from diffusing into theunderlying substrate 102. The conductive liner may be deposited by usingsuitable deposition process such as CVD, PVD, Atomic Layer Deposition(ALD) and/or the like.

A conductive material is then filled in the opening. The conductivematerial may be deposited by using CVD, PVD or ALD. The conductivematerial is deposited over the conductive liner to fill the contact plugopening. Excess portions of the conductive material are removed from thetop surface of the interlayer dielectric layer 115 by using aplanarization process such as CMP. The conductive material may becopper, tungsten, aluminum, silver, titanium, titanium nitride, tantalumand combinations thereof and/or the like.

FIG. 3 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 2 after an opening is formed the substrate in accordancewith an embodiment. A through via opening 302 may be formed into thefirst side 101 of the substrate 102. The through via opening 302 may beformed by applying and developing a suitable photoresist layer (notshown), and removing the portion of the substrate 102 that is exposed tothe desired depth. The through via opening 302 may be formed so as toextend deeper into the substrate 102 than the MOS transistor 200 formedwithin and/or on the substrate 102.

FIG. 4 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 3 after a liner layer is formed on the sidewalls and thebottom of the opening in accordance with an embodiment. Once the throughvia opening 302 has been formed within the substrate 102, the sidewallsand the bottom of the through via opening 302 may be deposited with aliner layer 122. The liner layer 122 may be formed of suitabledielectric materials such as TEOS, silicon nitride, oxide, siliconoxynitride, low-K dielectric materials, high-K dielectric materialsand/or the like.

The liner layer 122 may be formed using suitable fabrication processessuch as a PECVD process, although other suitable processes, such as PVD,a thermal process and/or the like, may alternatively be used.Additionally, the liner layer 122 may be formed to a thickness in arange from about 0.1 μm to about 5 μm.

FIG. 5 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 4 after a barrier layer is formed over the liner layer inaccordance with an embodiment. The barrier layer 124 may be deposited onthe liner layer 122 as well as the top surface of the interlayerdielectric layer 115. The barrier layer 124 may be formed of titanium,titanium nitride, tantalum, tantalum nitride, and combinations thereofand/or the like. The barrier layer 124 may be formed using suitablefabrication techniques such as ALD, PECVD, plasma enhanced physicalvapor deposition (PEPVD) and/or the like.

FIG. 6 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 5 after a seed layer is formed over the barrier layer inaccordance with an embodiment. The seed layer 126 may be may be formedof copper, nickel, gold, any combination thereof and/or the like. Theseed layer 126 may be formed by suitable deposition techniques such asPVD, CVD and/or the like. The seed layer 126 may have a thickness ofbetween about 50 Å and about 1,000 Å.

In addition, the seed layer 126 may be alloyed with a material thatimproves the adhesive properties of the seed layer 126 so that it canact as an adhesion layer. For example, the seed layer 126 may be alloyedwith a material such as manganese or aluminum, which will migrate to theinterface between the seed layer 126 and the barrier layer 124 and willenhance the adhesion between these two layers. The alloying material maybe introduced during formation of the seed layer 126. The alloyingmaterial may comprise no more than about 10% of the seed layer.

FIG. 7 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 6 after a dielectric layer is formed over the seed layerin accordance with an embodiment. A dielectric layer 702 is formed ontop of the seed layer 126. The dielectric layer 702 may be formed ofeither photoresist materials or non-photoresist materials. In accordancewith an embodiment, the dielectric layer 702 may be formed of generalphotoresist materials. The dielectric layer 702 may be formed bysuitable fabrication techniques such as spin coating and/or the like.

FIG. 8 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 7 after a patterning process is applied to the dielectriclayer in accordance with an embodiment. In consideration of the locationof metal lines and the through via, selective areas of the dielectriclayer 702 are exposed to light. As a result, the photoresist material inthe opening 302 is removed and a variety of openings (e.g., opening 802)are formed on top of the seed layer 126. The formation of the openingssuch as opening 802 in the dielectric layer 702 involves lithographyoperations, which are well known, and hence are not discussed in furtherdetail herein.

FIG. 9 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 8 after a conductive material is filled in the openings inaccordance with an embodiment. The through via opening as well as theopenings (e.g., opening 802) on top of the seed layer 126 may be filledwith a conductive material. The conductive material may comprise copper,although other suitable materials such as aluminum, alloys, tungsten,silver, doped polysilicon, combinations thereof, and/or the like, mayalternatively be utilized.

As shown in FIG. 9, the through via opening 302 is partially filled withthe conductive material. The conductive material may be filled in theopening 302 through an electroplating process. The electroplatingprocess is controlled so that the top surface 902 of the bottom portionof the through via is lower than the top surface 904 of the substrate102. FIG. 9 further illustrates the metal lines 912, 914 and 916 of thefirst metallization layer are formed at the same fabrication step as thethrough via.

In accordance with an embodiment, the metal lines 912, 914 and 916 areof a thickness in a range from about 0.5 um to about 10 um. Thesidewalls of the through via may be of a thickness similar to that ofthe metal lines 912, 914 and 916. The bottom portion of the through viamay be of a thickness about 10 to 50 times greater than the thickness ofthe metal lines 912, 914 and 916. It should be noted the thickness ratiobetween the bottom portion of the through via and the metal lines may beadjustable by controlling the electroplating process.

One advantageous feature of having the metal lines of the firstmetallization layer and the metal portions of the through via formed atthe same electroplating process is that the total production time of thesemiconductor device is reduced. Moreover, the through via is partiallyfilled with the conductive material. Such partially filled structurehelps to reduce the time of the electroplating process. In addition, theplanarization process commonly used in a conventional fabricationprocess may be saved. As a result, the cost as well as the productiontime of the semiconductor device is improved.

Another advantageous feature of the fabrication process described abovewith respect to FIG. 9 is that partially filled structure helps toresolve some common issues of the conventional structure. For example,in a via-first fabrication process, the through via is formed before theinterconnect structure. During the back-end-of-line (BEOL) process, thethermal stress of the BEOL process may cause reliability problems suchas copper popping and the like. By employing the partially filledstructure shown in FIG. 9, the copper popping problem may not lead to areliability issue because the through via is not fully filled withcopper. The dielectric material (not shown) filled in the through viamay function as a stress buffer to prevent the copper of the through viafrom popping out.

FIG. 10 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 9 after the remaining photoresist layer has been removedin accordance with an embodiment. The remaining photoresist layer shownin FIG. 9 may be removed by using suitable photoresist strippingtechniques such as chemical solvent cleaning, plasma ashing, drystripping and/or the like. The photoresist stripping techniques are wellknown and hence are not discussed in further detail herein to avoidrepetition.

In addition, the barrier layer and seed layer underneath the remainingphotoresist layer (shown in FIG. 9) may be removed by using a suitableetching process such as wet-etching, dry-etching and/or the like. Thedetailed operations of either the dry etching process or the wet etchingprocess are well known in the art, and hence are not discussed herein toavoid repetition.

FIG. 11 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 10 after an inter-metal dielectric layer is deposited inaccordance with an embodiment. The inter-metal dielectric layer 182 isformed over the interlayer dielectric layer 115. More particularly, theremaining opening (shown in FIG. 10) of the through via is filled withthe dielectric material through the deposition of the inter-metaldielectric layer 182. The inter-metal dielectric layer 182 may be formedof a low-K dielectric material such as fluorosilicate glass (FSG) and/orthe like. The inter-metal dielectric layer 182 may be formed by suitabledeposition techniques such as such as spin coating and/or the like.

One advantage feature of a through via filled with a combination of aconductive material and a dielectric material is that the dielectricmiddle portion may function as a stress buffer. Such a stress bufferhelps to prevent the through via from being damaged by thermal andmechanical stresses during the subsequent fabrication steps.

FIG. 12 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 11 after two additional metallization layers are formedover the first metallization layer in accordance with an embodiment. Asshown in FIG. 12, two additional metallization layers are formed overthe first metallization layer. While FIG. 12 shows two metallizationlayers formed over the first metallization layer, one skilled in the artwill recognize that more inter-metal dielectric layers (not shown) andthe associated metal lines and plugs (not shown) may be formed betweenthe metallization layers (e.g., layer 1206 and 1216) shown in FIG. 12.In particular, the layers between the metallization layers shown in FIG.12 may be formed by alternating layers of dielectric (e.g., extremelylow-k dielectric material) and conductive materials (e.g., copper).

It should further be noted that the metallization layers shown in FIG.12 are formed by a dual damascene process, although other suitabletechniques such as deposition, single damascene may alternatively beused. The dual damascene process is well known in the art, and hence isnot discussed herein.

The second metal line 1202 and the second plug 1204 are formed by a dualdamascene process. The second metal line 1202 is embedded in a secondinter-metal dielectric layer 1206, which is similar to the firstinter-metal dielectric layer 182. The second plug 1204 is formed in thefirst inter-metal dielectric layer 182. More particularly, the secondmetal line 1202 and the metal line 912 are coupled to each other throughthe second plug 1204. The second metal line 1202 and the plug 1204 maybe formed of metal materials such as copper, copper alloys, aluminum,silver, gold, any combinations thereof and/or the like. The third metalline 1212 and the third plug 1214 are formed in dielectric layers 1216and 1208 respectively. The third metal line 1212 and the third plug 1214are similar to the second metal line 1202 and the second plug 1204, andhence are not discussed to avoid repetition.

FIG. 13 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 12 after a passivation layer is formed on the top of theinter-metal dielectric layer in accordance with an embodiment. Thepassivation layer 154 is formed of non-organic materials such asun-doped silicate glass, silicon nitride, silicon oxide, siliconoxynitride, boron-doped silicon oxide, phosphorus-doped silicon oxideand/or the like. Alternatively, the passivation layer 154 may be formedof low-k dielectric such as carbon doped oxide and/or the like. Inaddition, extremely low-k (ELK) dielectrics such as porous carbon dopedsilicon dioxide can be employed to form the passivation layer 154. Thepassivation layer 154 may be formed through any suitable techniques suchas CVD.

As shown in FIG. 13, there may be an opening formed in the passivationlayer 154. The opening is used to accommodate a metal pad 156. As shownin FIG. 13, the metal pad 156 is embedded in the passivation layer 154.In particular, the metal pad 156 provides a conductive channel betweenthe metal lines (e.g., metal line 1212) and a post passivationinterconnect structure (not shown but illustrate in FIG. 24). The metalpad 156 may be made of metallic materials such as copper, copper alloys,aluminum, silver, gold and any combinations thereof, and/or multi-layersthereof. The metal pad 156 may be formed by suitable techniques such asCVD. Alternatively, the metal pad 156 may be formed by sputtering,electroplating and/or the like.

FIG. 14 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 13 after a first polymer layer is formed on the top of thepassivation layer in accordance with an embodiment. The first polymerlayer 158 is formed on top of the passivation layer 154. The firstpolymer layer 158 may be made of polymer materials such as epoxy,polyimide, polybenzoxazole (PBO), silicone, benzocyclobutene (BCB),molding compounds and/or the like. In accordance with an embodiment, thefirst polymer layer 158 may be formed of PBO. The first polymer layer158 may be made by suitable deposition methods known in the art such asspin coating.

FIG. 15 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 14 after a patterning process is applied to the surface ofthe first polymer layer in accordance with an embodiment. The patterningprocess may be implemented by using suitable patterning techniques suchas an etching process, a laser ablation process and/or the like.According to the shape and location of a redistribution line, an etchingprocess or a laser beam (not shown) may be applied to the top surface ofthe first polymer layer 158. As a result, a portion of the first polymerlayer 158 is removed to form an opening 1502.

FIG. 16 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 15 after a seed layer is formed on top of the firstpolymer layer in accordance with an embodiment. The seed layer 164 isformed over the first polymer layer 158. The seed layer 164 may comprisetwo portions, namely a bottom seed layer (not shown) and an upper seedlayer (not shown). The bottom seed layer may be a titanium layer, atitanium nitride layer, a tantalum layer, a tantalum nitride layerand/or the like. The upper seed layer may be formed of copper, copperalloys and/or the like. In accordance with an embodiment, the seed layer164 may be formed using any suitable techniques such as CVD, PVD and/orthe like.

FIG. 17 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 16 after a redistribution line is formed on top of theseed layer in accordance with an embodiment. As shown in FIG. 17, aconductive material may be filled in the opening (e.g., opening 1502shown in FIG. 15) to form the redistribution line 166. The conductivematerial may be copper, but can be any suitable conductive materials,such as copper alloys, aluminum, tungsten, silver, any combinationsthereof and/or the like. The redistribution line 166 may be formed bysuitable techniques such as an electro-less plating process, CVD,electroplating and/or the like.

As shown in FIG. 17, the redistribution line 166 connects the metal pad156. More particularly, the redistribution line 166 provides aconductive path between the metal lines (e.g., metal line 1212) and theinput/output terminal of the semiconductor device (e.g., the bump 176shown in FIG. 24). The operation principles of redistribution lines arewell known in the art, and hence are not discussed in detail herein.

FIG. 18 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 17 after a second polymer layer is formed over thesemiconductor device in accordance with an embodiment. The secondpolymer layer 162 is formed on top of the first polymer layer 158. Thesecond polymer layer 162 is made of polymer materials such as epoxy,polyimide, polybenzoxazole (PBO), silicone, benzocyclobutene (BCB),molding compounds and/or the like and/or the like. The second polymerlayer 162 may be deposited on the first polymer layer 158 using suitabledeposition techniques such as spin coating. The second polymer layer 158may be of a thickness in a range from about 4 um to about 10 um.

FIG. 19 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 18 after a patterning process is applied to the topsurface of the second polymer layer in accordance with an embodiment.The patterning process may be implemented by using lithography and etchprocesses. Alternatively, the patterning process may be implemented byusing a laser ablation process. According to the shape and location ofthe under bump metallization (UBM) structure (not shown but illustratedin FIG. 24), an etching process or a laser beam may be applied to thetop surface of the second polymer layer 162 to form an opening 1902.

FIG. 20 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 19 after a UBM seed layer is formed on top of the secondpolymer layer in accordance with an embodiment. The UBM seed layer 172is deposited on the second polymer layer 162. The UBM seed layer 172 maycomprise conductive materials such as copper and/or the like. The UBMseed layer 172 may be implemented by using suitable fabricationtechniques such as sputtering, CVD and/or the like.

FIG. 21 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 20 after a second conductive layer is formed on top of theUBM seed layer in accordance with an embodiment. As shown in FIG. 21, inorder to obtain a reliable UBM structure, additional conductivematerials may be deposited in a conformal manner on top of the UBM seedlayer 172 to form an additional conductive layer 174. The conductivematerial may be copper, but can be any suitable conductive materials,such as copper alloys, aluminum, tungsten, silver, any combinationsthereof and/or the like. The conductive layer 174 may be formed bysuitable techniques such as an electro-less plating process.

FIG. 22 illustrates a cross section view of the semiconductor deviceshown in FIG. 21 after an interconnect bump is formed on the UBMstructure in accordance with an embodiment. The interconnect bump 176provides an effective way to connect the semiconductor device withexternal circuits (not shown). In accordance with an embodiment, theinterconnect bump 176 may be a solder ball. The solder ball 176 may bemade of any of suitable materials. In accordance with an embodiment, thesolder ball 176 may comprise SAC405. SAC405 comprises 95.5% Sn, 4.0% Agand 0.5% Cu.

In accordance with another embodiment, the interconnect bump 176 may bea copper bump. The copper bump may be of a height of approximately 45um. The copper bump may be formed by using a variety of semiconductorpackaging technologies such as sputtering, electroplating and/or thelike.

FIG. 23 is a cross sectional view of the semiconductor deviceillustrated in FIG. 22 after a thinning process has been applied to thesecond side of the substrate in accordance with an embodiment. Accordingto the fabrication processes of through vias, the second side (a.k.a.backside) of the substrate 102 is thinned until the conductive materialof the through via is exposed.

The thinning process may be implemented by using suitable techniquessuch as grinding, polishing and/or chemical etching, a combination ofetching and grinding techniques. In accordance with an embodiment, thethinning process may be implemented by using a CMP process. In the CMPprocess, a combination of etching materials and abrading materials areput into contact with the backside of the substrate and a grinding pad(not shown) is used to grind away the backside of the substrate 102until the conductive material of the through via is exposed.

FIG. 24 illustrates a cross section view of the semiconductor deviceshown in FIG. 23 after a backside contact is formed on the second sideof the substrate in accordance with an embodiment. A cleaning processmay be employed to remove any remaining residue such as copper oxide onthe backside of the substrate 102, a backside contact 2402 may be formedon the second side of the substrate 102 in electrical contact with theconductive material located within the through via.

The backside contact 2402 may comprise a conductive layer (not shown)and an electro-less nickel immersion gold (ENIG) layer (not shown). Theconductive layer may comprise aluminum and may be formed through asputter deposition process. However, other materials, such as nickel,copper and/or the like may alternatively be used. In addition, otherformation processes such as electroplating or electro-less plating mayalternatively be employed to form the conductive layer. The conductivelayer may be formed with a thickness of between about 0.5 μm and about 3μm.

The formation of the conductive layer may be followed by an ENIG processto form the ENIG layer. The ENIG process may comprise cleaning theconductive layer, immersing the substrate 102 in a zincate activationsolution, electrolessly plating nickel onto the conductive layer, andelectrolessly plating gold onto the nickel.

Alternatively, the formation of the conductive layer may be followed byother conductive layers similar to the ENIG layer. For example, theconductive layer may be an electro-less nickel electro-less palladiumimmersion gold (ENEPIG) layer, which includes a nickel layer, apalladium layer on the nickel layer and a gold layer on the palladiumlayer. Furthermore, the ENIG or ENEPIG layer may be replaced by othersimilar conductive layers such as an electro-less nickel electro-lesspalladium (ENEP) layer, a direct immersion gold (DIG) layer and/or thelike.

A backside passivation layer 2404 may be partially formed over thebackside contact 2402 in order to seal and protect the backside contact2402. The backside passivation layer 2404 may comprise a dielectricmaterial such as an oxide or silicon nitride, although other suitabledielectrics, such as a high-k dielectric, may alternatively be used.

The backside passivation layer 2404 may be formed using a PECVD process,although any other suitable process may alternatively be used. Once thebackside passivation layer 2404 is deposited on the second side of thesubstrate, in order to expose at least a portion of the backside contact2402, a patterning process may be applied to the backside passivationlayer 2404. A suitable etching technique may be applied to the backsidepassivation layer 2404 so that the backside contact 2402 is exposed. Asa result, exterior devices (not shown) may be connected to the backsidecontact 2402.

Although embodiments of the present disclosure and its advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the present disclosure, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to the presentdisclosure. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, or steps.

What is claimed is:
 1. A method comprising: forming a trench extendingthrough an interlayer dielectric layer over a substrate and partiallythrough the substrate; depositing a photoresist layer over the trench,wherein the photoresist layer partially fills the trench; patterning thephotoresist layer to remove the photoresist layer in the trench and forma metal line trench over the interlayer dielectric layer; filling thetrench and the metal line trench with a conductive material to form avia and a metal line, wherein an upper portion of the trench is free ofthe conductive material; and depositing a dielectric material over thesubstrate, wherein the dielectric material is in the upper portion ofthe trench.
 2. The method of claim 1, further comprising: depositing aliner layer on sidewalls and a bottom of the trench; depositing abarrier layer over the liner layer, wherein the barrier layer is incontact with a top surface of the interlayer dielectric layer; anddepositing a seed layer over the barrier layer.
 3. The method of claim2, wherein: the metal line and the interlayer dielectric layer areseparated by the liner layer and the barrier layer.
 4. The method ofclaim 1, wherein: after filling the trench and the metal line trenchwith the conductive material, the conductive material forms a U-shapedconductive structure in the trench.
 5. The method of claim 4, wherein: athickness of a bottom portion of the U-shaped conductive structure isabout ten times greater than a thickness of a sidewall portion of theU-shaped conductive structure.
 6. The method of claim 1, wherein: atopmost surface of the via is substantially level with a topmost surfaceof the metal line.
 7. The method of claim 1, wherein: the conductivematerial is copper.
 8. A method comprising: forming a trench extendingpartially through a substrate; depositing a photoresist layer over thetrench, wherein the photoresist layer is on a bottom and sidewalls ofthe trench; patterning the photoresist layer to form a metal linetrench; filling the trench and the metal line trench with a conductivematerial to form a first metal line in the metal line trench and asecond metal line extending into the trench along a sidewall of thetrench; and depositing a dielectric material over the substrate, whereinat least a portion of the dielectric material is in the trench andsurrounded by the second metal line.
 9. The method of claim 8, furthercomprising: forming an interlayer dielectric layer over the substrate,wherein the trench extends through the interlayer dielectric layer. 10.The method of claim 9, further comprising: depositing a liner layer onsidewalls and a bottom of the trench, wherein a topmost surface of theliner layer is substantially level with a topmost surface of theinterlayer dielectric layer; depositing a barrier layer over the linerlayer, wherein the barrier layer is in contact with the topmost surfaceof the interlayer dielectric layer; and depositing a seed layer over thebarrier layer.
 11. The method of claim 8, wherein: a top surface of thefirst metal line is substantially level with a top surface of the secondmetal line.
 12. The method of claim 8, wherein: a portion of the secondmetal line in the trench is a U-shaped structure.
 13. The method ofclaim 12, wherein: a thickness of a bottom portion of the U-shapedstructure is greater than a thickness of a sidewall portion of theU-shaped structure.
 14. The method of claim 8, wherein: a bottommostsurface of the dielectric material is lower than a topmost surface ofthe substrate.
 15. A method comprising: forming a trench in a substratecomprising a transistor, wherein a bottom of the trench is lower than abottom of a drain/source region of the transistor; depositing aphotoresist layer over the trench, wherein the photoresist layerpartially fills the trench; patterning the photoresist layer to removethe photoresist layer in the trench and form a metal line trench overthe drain/source region of the transistor; plating a conductive materialover the trench and the metal line trench to form a via in the trenchand a metal line in the metal line trench; and depositing a dielectricmaterial over the substrate, wherein at least one portion of thedielectric material is in the trench and surrounded by the metal line.16. The method of claim 15, wherein: the photoresist layer includes abottom portion over a bottom of the trench and a sidewall portion alonga sidewall of the trench.
 17. The method of claim 15, furthercomprising: depositing a liner layer on sidewalls and a bottom of thetrench; depositing a barrier layer over the liner layer; and depositinga seed layer over the barrier layer.
 18. The method of claim 15,wherein: after the step of depositing the dielectric material over thesubstrate, the via comprises a U-shaped conductive structure and adielectric middle portion surrounded by the U-shaped conductivestructure.
 19. The method of claim 15, further comprising: forming aninterlayer dielectric layer over the substrate, wherein the via extendsover a top surface of the interlayer dielectric layer.
 20. The method ofclaim 15, wherein: the transistor is between a first isolation regionand a second isolation region, and wherein a bottom of the trench islower than bottoms of the first isolation region and the secondisolation region.